Muffler with cutout and removable baffle



Dec. 27, 1949 J. A. CHISTMAN MUFFLER WITH UTOUT AND REMOVABLE BAFFLE Filed Sept. 16, 1947 Enign l the muiiler;

Patented Dec. 27, 1949 UNITED STATES PATENT OFFICE- MUFFLER WITH CUTOUT AND REMOVABLE BAFFLE The present invention relates to muiiiers for internalcombustion engines, and has particular reference to an improved muffler adapted for attachment to the exhaust pipe or stack of a motorcycle engine, although not specifically limited to such adaptation.

Generally, the present day motorcycle is characterized by the undesirable and distracting noise produced by the explosions of its engine, and although particular attention is given to other vehicles, such as automobiles, to eliminate excessive engine noise, no concerted effort has been put forth to reduce the excessive, and in some instances, the unlawful noise produced by the ordinary motorcycle engine.

It is therefore, an object of this invention to provide .a structurally simple, yet mechanically efficient muffler for motorcycles which functions to selectively reduce the noise produced by the eX- plosions within the associated engine, yet does not impair the efficiency of the engine to any material extent by creating back pressures within the exhaust system.

It is another object of this invention to provide an improved muiiier for internal combustion engines which consists of an elongated tube having an internal chamber or passageway progressively enlarged from the engine exhaust pipes outwardly of the tube to provide an increased volume for the expansion of exhaust gases emanating from the exhaust pipes of an engine, and in which is mounted a ycable-controlled butteriiy valve for selectively opening or restricting the passageway to absorb or baffle the sound produced by the explosions within the associated engine, and which is further provided with a second sound baiiie or mute detachably carried in the outer end of the tube to further reduce or deaden the noise produced by engine explosions.

For a further and more detailed understanding of the present invention and the additional.

objects and advantages thereof, reference is made to the following description and the accompanying drawing wherein:

Fig. I is a side elevational view of the present improved muilier operably installed upon an associated motorcycle, shown in broken lines;

Fig. 2 is an enlarged side elevational view of Fig. 3 is an enlarged. fragmentary vertical tional view taken through the discharge end of the muier disclosed in Fig. 2;

AFig. 4 is a transverse vertical sectional view taken along a Yplane indicatedv by the line 4-4 of Fis- ,3:

vlili Fig. 5 is an end elevational view of the muffler, disclosing particularly the removable mute positioned in the discharge end thereof;

Fig. 6 is a fragmentary vertical sectional view taken through the discharge end of the muilier, and a modified form of mute or sound baiile;

Fig. "l is an end elevational view of the modied type of mute disclosed in Fig. 6.

Referring now to the drawing, the numeral I designates a motorcycle having an engine 2 which is provided with relatively short exhaust pipes or stacks 3 leadingseparately from each of the cylinders of the engine, or from the exhaust manifold thereof. Connected with the outer ends of each of the exhaust pipes 3, by means of suitable pipe connections 4, is an elongated and tapered tube 5, formed at its inner end with the previously mentioned pipe connections 4, and at its opposite outer end with a relatively enlarged discharge opening 6. The tube 5 is further provided with a straight internal chamber or passageway 'l leading from the pipe connections 4 to the discharge opening 6 of the tube, and being progressively enlarged in cross-section from the inner-to the outer end of the tube.. The-tube 5 is provided upon itsupper surface with a laterally extending attaching bracket 8 by which the tube may be supported and connected with a frame member of the associated motorcycle l,

In cross section, the tube 5 andits passageway 1 possess a generally circular configuration, and positioned within the passageway of the tube adjacent the discharge end thereof is a circular butterfly valve 9 whose diameter is substantially y less than the diameter of the internal passageway l. The valve 9 is carried upon a centrally disposed shaft IU extending transversely of the tube andvrotatably supported within a pair of trunnion supports Il formed in the outer wall of the tube. The plane of the trunnion supports .l i is disposed slightly below the major horizontal axis of the tube, so that the bntterfiy valve .9 is disposed eccentrically of the circular passageway 1, with the lower surface of the butterily engaging the lower inner wall of the tube, as the former approaches a substantially vertical position. The centrally disposed shaft l0 extends outwardly from one of the trunnion supports Il, and is connected with a rocking lever l2 whose outer end is formed with an opening through which the outer end a remotely controlled exiblecable i8 may be passed and sesv cured .to impart rocking movement to the lever I2, and tilting movement to the butterfly valve Swith respect to the-circular passageway l.

tube.

shown particularly in Figs. 3 and 4 of the drawings, the buttery 9 is movable, upon actuation of the rocking lever I2, between positions completely opening and partially closing the passageway 'L As the butterfly 9 approaches a substantially vertical position, as shown in Fig. 3, its lower edge strikes or drags the lower surface of the tube to prevent further rocking movement of the butterfly past the position shown in Fig. 3. In this position, the butterfly presents a sound baille, and exhaust gases passing outwardly of the tube 5 are deflected by the butterfly and are forced to pass between the l space defined by the upper edge oi the butterfly and the upper inner wall of the tube. Conversely, as the rocking lever l2 is actuated to position the butterfly in a horizontal plane, or along the longitudinal axis of the tube, exhaust gases are free to pass without obstruction from the pipe connection to the discharge end of the Due to the fact that the passageway of the tube is increasingly enlarged toward the discharge end thereof, the restriction caused by the butterfly valve 9. as the same approaches a vertical position, will not materially affect the eiliciency of the associatedengine, because the area of the passageway between the upper edge or section of the butterfly and the inner surface of the tube wall closely approximates the area of the two exhaust stacks 3 of the engine, and therefore has approximately the same eifect as if the exhaust pipes` were extended through an untapered tube. Further. by increasing the volume through which the exhaust gases may pass from the exhaust pipes. the sound of the explosions within the engine are materially deadened, with the pitch of the explosions being reduced to a considerably lower note.

Detachably carried in the outer discharge opening 5 of the tube, is a substantially circular and perforate sound baffle or mute i4. The side walls of the mute are inwardly tapered to correspond to the taper ofthe outer end of the tuhe` in order that a close frictional fit may be obtained between the mute and the discharge opening of the tube. Further, the `mute i4 is held in position by means of ascrew-threaded bolt l5 introduced through the wall of the tube and receivable in a cooperatively screw-threaded opening formed in the side walls of the mute. The mute is provided with. an arcuate handle member H5 extending from the rearward perforate face. and affording a handle by which the mute may be easily removed and replaced within the discharge opening E of the tube. The perforate wall of the mute lli serves as an additional sound baiile. but at the same time provides for the free passage of exhaust gases therethrough.

In operation.y the removable mute Il! is used for normal city driving, where a minimum of objectionable noise is desired. With the mute i4 in its position within the discharge opening o f the tube, there is little need for closing the butterily 9, except when passing through zones or districts where extreme quiet is required, in such an instance, the butterfly valve 9 may be actuated to partially block the passageway l of the tube, and to further reduce the noise of the associated engine. When driving upon the highway, par ticularly at relatively high speeds, and where maximum efficiency of the engine is required or desired, the mute i4 is removed altogether from the discharge opening of the tube, and the buttery valve 9 is actuated in accordance with the desires of the driver. For instance, when passing through a town or city, or other populated area, the butterfly valve 9 provides a convenient means for temporarily decreasing the noise of the engine, but when once again upon the highway the saine may be opened to provide for maximum efficiency within the engine.

Figs. 6 and '7 of the drawing disclose a modified type of mute which is removably positioned within the discharge opening 6 of the tube. In this form, the mute comprises an outwardly tapered body provided with three triangularly disposed fins Il. This mute is also provided with a relatively restricted discharge opening I8 at the outermost end thereof, and a relatively elongated open slot I9 formed in the lower under surface of the mute. The opening I8 and slot I9 provide for the discharge of exhaust gases from within the main tube 5, and due to the tapered configuration of the mute body, air turbulence is set up around the rearwardly projecting mute, particularly at relatively high speeds, which turbulence aids in the withdrawal of exhaust gases from within the mute and tube, thereby tending to increase the ei'liciency of the associated engine through the quick removal of the spent exhaust gases therefrom, or even to the extent of creating reduced pressures at the rearward end of the tube 5.

In view of the foregoing, it will be seen that the present invention provides a useful and mechanically efficient muier for internal combustion engines, the same functioning to selectively control the degree and pitch of the sound emanating from the explosions within the associated engine, yet at the same time functioning in a manner so as not to reduce the overall efficiency of the associated engine by creating an undesirable back pressure within the exhaust system. The invention is further characterized by its structural simplicity, and its consequent economy of manufacture and maintenance.

While present preferred forms of the present invention have been disclosed in detail, it will be manifest that various modifications as to details of construction are possible without departing from the spirit of the invention or the scope of the following claims.

I claim:

l. A muilier for internal combustion engines having an exhaust pipe, comprising an elongated tube formed at one end with an exhaust pipe connection and at its opposite end with an exhaust discharge opening, said tube being formed with a tapered internal passageway having a circular cross-sectional configuration through which exhaust gases may pass, the passageway of said tube being progressively enlarged in crosssection from the pipe connection end thereof to the discharge opening of the tube, and a circular butterfly valve positioned eccentrically within the passageway of said tube adjacent the discharge end thereof and movable therein between positions opening and partially closing the passageway.

2. In a muffler for internal combustion engines having an exhaust pipe, an elongated openended tube connected at one of its ends with the.

exhaust pipe of an engine, said tube being formed with a tapered bore progressively enlarged in cross-section from, the exhaust pipe-receiving end to the opposite end thereof, and a cable-controlled butterfly valve positioned within the bore of said tube and movable therein between positions opening and partially closing the bore, said valve having an area substantially less than the cross-sectional area oi' 'the bore of said tube where said valve is positioned, whereby to provide for substantiallyrunrestricted passage of gases through said tube when said valve occupies its position of partial borev closure.

3. In a muiller for internal combustion engines having an exhaust pipe, an elongated openended tube connected at one of its ends with the exhaust pipe of an engine, said tube being formed with a tapered bore progressively enlarged in cross-section from the exhaust pipereceiving end to the opposite end thereof, and a cable-controlled butterfly valve positioned eccentrically of the bore of said tube and movable therein between positions opening and partially closing the bore.

4. In a muiller for internal combustion engines having an exhaust pipe, a single longitudinally tapered tube formed at one end with an exhaust pipe-receiving opening and at its opposite end with a discharge opening and an internal longitudinally and continuously tapered passageway connecting said openings and progressively enlarged in cross-section from the exhaust pipereceiving opening to the discharge opening, and

ajbutterily valve mounted within the passageway ofv said tube adjacent the discharge end thereof for movement between a position substantially parallel to the axis of said tube and a position substantially perpendicular to the longitudinal axis of said tube, said valve having a substantiallysmaller area than the cross-sectional area of the passageway of said tube where said valve is positioned whereby to provldepspace between said valve and said tube at leastfequal to the area ofl said pipe-receiving opening at any position of said valve within said passageway.

JOHN A. CHRISTMAN.

REFERENCES CITED The following references are `of record in the le of this patent:

UNITED STATES PATENTS Number Name Date 1,023,225 Shlosberg Apr. 16, 1912 1,375,621 Wright Apr. 19, 1921 1,615,147 Taylor Jan. 18, 1927 1,829,737 Compo Nov. 13, 1931 2,404,589 Monaghan July 23, 1946 

